Hydraulic jack with safety means



March 14, 1967 J- w. JANSZ 3,309,062

HYDRAULIC JACK WITH SAFETY MEANS Filed May 10, 1965 f7 75 m mvro/e Arm/ms;

Patented Mar. 14, 1967 3,309,062 HYDRAULIC JACK WITH SAFETY MEAN Joost Werner Jansz, The Hague, Netherlands, assignor to Richard Costain Limited, London, England, a British company Filed May 10, 1965, Ser. No. 454,367 Claims priority, application Netherlands, May 8, 1964, 64/ 05158 4 Claims. (Cl. 254-93) The present invention relates to hydraulic jack of which the distance through which the jack is raised can be accurately controlled, and is particularly suitable for use where the jack has to perform precise lifting steps, for example in raising a building structure by a plurality of jacks which have to be operated in a manner which will maintain the building structure substantially upright while it is being raised.

The present invention consists in a hydraulic jack wherin a nut, rotatably mounted on a screw thread provided on the jack piston rod or a rod movable therewith, is turned by a pawl and ratchet mechanism or the like actuated by an auxiliary hydraulic device which is hydraulically connected with the jack cylinder so that, as the jack is raised, the nut is turned so that it bears against a part which is fixed relative to the jack cylinder, the movement of the pawl and ratchet mechanism actuating means for controlling the stroke of the jack. The means controlling the strokeof the jack conveniently comprise one or more electric switch means which cooperate with the pawl and/ or the ratchet to control a valve regulating the supply of hydraulic fluid to the jack.

As the nut continuously bears against the jack cylinder or a part which is fixed relative thereto, the nut also serves as a locking device which safeguards the jack against untimely lowering in the event of failure of the hydraulic pressure.

In order that the invention may be more clearly understood, an embodiment thereof will now be described with reference to the accompanying drawing, in which:

FIGURE 1 shows schematically a longitudinal section of a hydraulic jack according to the invention.

FIGURE 2 is a fragmentary plan view, on a larger scale, taken on line IIII in FIGURE 1.

The hydraulic jack 1 shown comprises a work-cylinder 2 in which slides a piston 3 secured to a piston rod 4. The jack 1 is of the angle-acting type, liquid under pressure for lifting the load being supplied to one side 5 of the piston 3 from a source 6 through pipes 7, 8.

The piston rod 4 is provided with a screw thread on which is threaded a nut 9. The nut 9 is movable by auxiliary mechanism which controls the jack stroke, consisting of ratchet teeth 10 provided around the nut 9 and cooperating with a pawl 11, which is actuated by an auxiliary liquid-actuated single-acting cylinder 12 provided with a piston 13. To rotate the nut 9 by means of pawl 11 and ratchet teeth 10, liquid under pressure from source 6 is supplied to the side 14 of the piston 13 through pipes 7 and 15. A common control valve 16 provides for simultaneous supply of pressure liquid from source 6 through pipes 7 and 8 to the jack cylinder 2, and through pipes 7 and 15 to the auxiliary cylinder 12. The control valve 16 is actuated by electrical switches 17, 18 which respectively cooperate with the pawl 11.

After each partial rotation of the nut 9, corresponding to a selected jack stroke, the switch 17 is actuated by pawl 11 which latter effects a change over of control valve 16 whereby the pressure liquid is directed into a return conduit and the pressure in pipes 7, 8 and 15 is released. The return movement of the pawl 11 and the piston 13 is effected mechanically by a compression spring 19 which may, for example, be incorporated in the cylinder 12.

At the end of the return stroke, the switch 18 is actuated by the pawl 11 and changes over the control valve 16 to its previous position whereupon pressure can again be built up in pipes 7, 8. 15.

The nut 9 acts as a locking nut and effects a follow-up movement during the jack stroke by the operation of the auxiliary mechanism whereby to control of the jack stroke, and applies itself against the jack cylinder jacket 2 so that the jack 1, whatever be its position is safeguarded from untimely return if the pressure in the system should fail for any reason.

Instead of the switch 17 for changing over of control valve 16, a switch as shown at 20 may be used, which is actuated by the angular displacement of the teeth 10 on the nut 9, for example actuated by the respective tips of the teeth to provide a jack stroke corresponding to the rotation of the nut 9 by the pitch of one tooth, or a combination of both switches 17 and 20 is possible, switch 17 then providing an additional safety function.

It should be noted that the jack cylinder 2 is connected via a non-return valve 21 with pipes 7, 8 and 15, whereby upon release of the pressure in pipes 7, 8 and 15 the auxiliary piston 13 is allowed to return while the pressure in the jack cylinder 2 is maintained.

A switch 22 acts as a safety contact for ensuring firm application of locking nut 9 against the jack cylinder jacket 2. The jack 1 is provided with a relief system (not shown) and means, such as a worm wheel may be provided on a zone of the periphery of nut 9 whereby the nut 9 may be turned backwards, for example by means of a worm fixed in a hand drilling machine or the like, for lowering the jack.

The auxiliary mechanism for controlling the jack stroke described above is actuated hydraulically and mechanically. It could also be operated entirely hydraulically by using an auxiliary cylinder 12 which is double-acting.

Several hydraulic jacks according to the invention may act as a system, with each jack in the system having its individual supply of pressure liquid, and all electrical switch means 18 actuated by the return of the auxiliary pistons being connected in series, so that in all jacks the building up of the pressure in the pipes 7, 8 and 15 starts simultaneously. In this way it is possible to operate the jacks, which may be hydraulically independent and subject to diflerent loads, at exactly the same average lifting speed.

Further, the operation of more than one jack from a common hydraulic supply is possible, in which case, in principle, only one of such jacks need be provided with an electrical switch means such as 20, provided that the jacks are equally loaded.

I claim:

1. Hydraulic jack comprising a jack cylinder having an inlet for hydraulic pressure fluid, a piston movable in said cylinder, a nut rotatably mounted on a screw thread provided on a rod movable with the piston, drive means for turning said nut, as the jack is raised, in a direction to urge the nut against a part which is fixed relative to the cylinder, means for interrupting the supply of hydraulic pressure fluid to said inlet, and means responsive to the turning of the nut through an angle corresponding to a predetermined increment of lift for actuating said interrupting means to interrupt the supply of hydraulic pressure fluid to said inlet.

2. A jack as claimed in claim 1, wherein said drive means comprises a pawl cooperating with ratchet teeth associated with the nut, and an auxiliary hydraulic motor connected to the supply of hydraulic pressure fluid to the jack cylinder inlet, said auxiliary hydraulic motor being connected to drive the pawl to turn the nut when hydraulic fluid pressure is supplied thereto and to the jack cylinder inlet, and means for moving the auxiliary 3 hydraulic motor and the pawl in the reverse direction when the supply of hydraulic pressure fluid is interrupted.

3. A jack as claimed in claim 2, including at least one electric switch means cooperating with the pawl and ratchetand connected to actuate a control valve in a supply pipe through which hydraulic pressure fluid is supplied to said jack-cylinder inlet and to said auxiliary hydraulic motor.

4. A jack asclaimed in claim 3, wherein a nonreturn 4' References Cited by the Examiner UNITED STATES PATENTS 1,223,621 4/1917 Scheren'zel 91-43 2,201,189 5/1940 Makaroff et a1 1878.49 2,875,980 3/1959 Grace 25493 3,104,593 9/1963 Clifton et a1. 9217 WILLIAM FELDMAN, Primary Exam'ziner.

valve is connected between. said supply pipe and the 10 OTHELL M. SIMPSON, Examiner.

jack cylinder inlet. 

1. HYDRAULIC JACK COMPRISING A JACK CYLINDER HAVING AN INLET FOR HYDRAULIC PRESSURE FLUID, A PISTON MOVABLE IN SAID CYLINDER, A NUT ROTATABLY MOUNTED ON A SCREW THREAD PROVIDED ON A ROD MOVABLE WITH THE PISTON, DRIVE MEANS FOR TURNING SAID NUT, AS THE JACK IS RAISED, IN A DIRECTION TO URGE THE NUT AGAINST A PART WHICH IS FIXED RELATIVE TO THE CYLINDER, MEANS FOR INTERRUPTING THE SUPPLY OF HYDRAULIC PRESSURE FLUID TO SAID INLET, AND MEANS RESPONSIVE TO THE TURNING OF THE NUT THROUGH AN ANGLE CORRESPONDING TO A PREDETERMINED INCREMENT OF LIFT FOR ACTUATING SAID INTERRUPTING MEANS TO INTERRUPT THE SUPPLY OF HYDRAULIC PRESSURE FLUID TO SAID INLET. 